Since your question falls under the heading of gender relations, separation/divorce I can only surmise one person in the marriage is affraid the other may decide to walk away. In my opinion a divorce is nothing more than one or both people reaching the conclusion that a mistake was made.
There is no amount of communcation or work that can overcome being with someone who does not want you want.
When it's all said and done life is a personal journey. Each of us gets to choose our own friends, lovers, and spouse. The only person we can control is ourselves. I personally would not want anyone to stay with me who did not want to be with me. I suspect that is what the writer was saying when he said, "If you love someone set them free and if they don't come back it was not meant to be."
My take is in order for him or her to be "the one" they would have to see you as being "the one". The very definition of "soulmates" is having mutual feelings for one another and wanting the same things for their relationship.